Warhammer Colonials is a set of amendments to Warhammer 40K for 19th Century colonial warfare. from Jervis Johnson himself.
Warhammer Napoleonics is a set of stat lines and rules amendments for fighting battles of the Napoleonic Wars using the popular Warhammer rules.
Games Workshop’s Warhammer miniatures rules have been adapted to a wide variety of other periods. You can get the Warhammer ‘Nam rules by joining the Yahoo Group.
The Gemini rules for Warhammer 40,000 are essentially a set of house rules for Games Workshop’s flagship product.
I think that the author is correct in his premise — that the Rogue Trader rules were perhaps the best.